The invention relates to a multi-cylinder internal combustion engine with at least two cylinder banks each of which includes an exhaust system with a catalytic converter wherein one of the cylinder banks can be made inoperative during partial load operation of the engine.
DE 196 11 363 C1 discloses a multi-cylinder internal combustion engine including two cylinder banks each having several cylinders wherein one of the cylinder banks is always operative while the other can be inactivated during partial load operation. Each cylinder bank is provided with an exhaust system including a catalytic converter. Downstream of the catalytic converters, the separate exhaust gas systems are joined in a common exhaust pipe section, which is then again split to feed two mufflers through which the exhaust gas is discharged to the atmosphere.
During partial load operation, a vacuum is generated in the exhaust system associated with the inactivated cylinder bank upstream of the respective catalytic converter so that the exhaust gas of the operational cylinder bank first flows through its associated catalytic converter. Then however it is returned, by way of the common exhaust pipe section and the catalytic converter of the inactivated cylinder bank, to the cylinders of the deactivated cylinder bank. In this way, the catalytic converter of the deactivated cylinder bank is maintained at operating temperature also during partial load operation so that the exhaust gas emissions are maintained at minimum level when the inactivated cylinder bank is reactivated.
It is the object of the present invention to reliably maintain the catalytic converter of the cylinder bank, while inactivated during partial load operation, at operation temperature in a simple manner, specifically without the need for generating a vacuum upstream of the catalytic converter of the inactivated cylinder bank.